Channel Assignment for Wireless Networks Reducing Interference
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Solution Overview
Problem
Current wireless network channel assignment methods fail to effectively reduce interference and increase capacity, particularly in systems with channel reuse of 1, as they either reduce throughput or lead to increased collisions with higher user loading.
Innovation Solution
Intelligently assigning channels based on signal strength between mobile stations and base stations, with optional power control to optimize user capacity and reduce interference, by pairing mobile stations with the strongest signal on one channel and the weakest signal on another, and designating preferred users for minimal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If N=1 reuse systems use all channels in every cell, then channel utilization is improved, but interference between mobile stations increases
Solution Approach 1:
The patent applies local quality by assigning channels based on the specific signal strength conditions of each mobile station. Mobile stations are categorized into groups (e.g., those with strongest signal, weakest signal) and assigned channels locally optimized for their interference conditions, rather than using a uniform channel assignment across all cells.
Solution Approach 2:
The patent converts the harmful interference effect into a benefit by intentionally assigning mobile stations experiencing strong interference on one channel to different channels, while assigning mobile stations with weak signal to channels where they experience less interference. This transforms the interference problem into a criterion for intelligent channel selection.
2Reliability
If CDMA spreading is used to extract signals from interference, then signal reliability is improved, but overall throughput decreases
Solution Approach 1:
The patent extracts the essential requirement for signal reliability without taking out the harmful spreading operation. Instead of using spreading to combat interference, the invention extracts signals by assigning them to different channels where interference is minimized, thereby maintaining reliability without the throughput penalty of spreading.
3Reliability
If frequency hopping with random channel selection is used, then collision probability is reduced for few users, but collision possibility increases with higher loading
Solution Approach 1:
The patent applies preliminary action by pre-categorizing mobile stations into groups based on their signal strength characteristics before channel assignment. This preliminary classification enables the system to make informed channel assignments that prevent collisions even under high loading conditions, rather than relying on random selection that fails when all users are active.
4Object-affected harmful factors
If intelligent channel assignment based on signal strength is implemented, then interference is reduced, but system complexity increases
Solution Approach 1:
The patent reduces complexity by segmenting mobile stations into discrete groups (e.g., those with strongest signal, weakest signal, intermediate signal) and assigning channels to each group according to fixed rules. This segmentation transforms the complex problem of individualized channel optimization into a manageable set of category-based assignments.
Data Source
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AI summary
There is disclosed a system and method for improving wireless system capacity by reducing collisions where the Signal to Interference Ratio (SIR) is high in systems having a channel reuse of 1. By ordering the channel assignment in each of the interfering cells according to a pattern, for example, according to the distance from a base station (determined by power levels), the mobile stations will become paired on the same channel in a manner to reduce interference between them. In one embodiment, this intelligent assignment is accomplished by assigning mobile stations in one cell such that the mobile station having the strongest signal is assigned channel A while in the interfering cell the mobile station with the weakest signal is assigned to channel A. In another embodiment, certain preferred mobile stations are assigned either interference- free channels or channels paired with weak interference mobile stations.